Method of plodding soap



Sept. 3, 1940- B. STRAIN METHOD OF PLODDING SOAP Filed NOV. 9, 1957 TNVENTOR, 5in/cs SUM/N.

BY MCT@ ATTORNEYS. v

Patented Sept. 3, 1940 UNITED STATES PATENT OFFICE METHOD OF PLODDING SOAP a corporation of Ohio Application November 9, 1937, Serial No. 173,694

2 Claims. (Cl. 252-667) This invention relates to a method for plodding plastic milled soap whereby improved milled soap products are obtained.

It is an object of my invention to produce a milled soap bar with a minimum tendency toward cracking, whether immediately after preparation, during storage of the bar, or during washstand use.

The presence of cracks and their prevention in milled toilet soap bars has always been a problem with soap manufacturers. Such cracks tend to form cleavage planes and thereby cause the soap bar to break apart in use. When the cracks occur on the surface of the bar dirt accumulates therein, thereby giving the bar a bad appearance andy making the same unsightly for use on the Washstand. Cracks may be present in a freshly plodded bar,`and may be seen on cutting the bar open. In some cases, however, the cracks develop or become more apparent on aging or when the bar is used with water. Cracks seem to be due to the imperfect welding together of the individual small masses of soap which are compressed, or plodded to form the bar. These small masses are usually in the form of flakes, ribbons, or spaghetti shaped masses. 'Ihe imperfect welding is caused by lack of proper plasticity, or non-uniformity, in the masses when compressed, which conditions may be caused by uneven drying, occlusion of air between the soap particles, low temperature of plodding, or difference in dryness or crystalline structure between the surface and the interior of the small masses plodded.

Some soap manufacturers have attempted to overcome undesirable cracks and crack formation in milled soap cakes by incorporating in the fat formula fatty materials whose soaps possess a lesser tendency to crack. Other manufacturers have more or less eliminated crack formation by employing fat formulas of low titer, or melting point. My method of crack elimination, which is applicable to any soap including that made with high titer fats, will be clearly understood from the following description.

In the drawing,

Figure 1 illustrates the essential features of one form of device which may be employed in the practice of my invention; and

Figure 2 illustrates the essential features of another form of device which may be employed in the practice of my invention.

In the practicing of the invention with either device, the plastic milled soap in particle form is fed by hopper I9 to the barrel I I in which is suitably located a shaft I2 having thereon a worm I3 operated by some source of power either directly or through pulley It. The inner surface of the barrel I I is contacted by the flights on the worm I3 thereby forming a bearing surface and making unnecessary the use of a shaft bearing at the end opposite the driving end of the shaft.

'Ihe milled soap particles are picked up by the worm I3, compressed and carried forward with a kneading action. That portion of the barrel II occupied by the worm I3, indicated at I5 in the drawing, I refer to as the deaerating zone, because in this zone the soap is compressed and kneaded while being carried forward so as to work out substantially all of the air entrapped between the individual particles of soap and to allow said air to escape through the soap inlet. The deaerated soap is then forced by means of the pressure developed by the worm through the remainder of the plodderwhich is referred to herein broadly as the Welding zone and which comprises a converging section, indicated generally at I6, and an extension Il. An extruding die I8 through which the soap issues in the form of a continuous rod in condition for cutting and stamping is located on the exit end of the welding zone of the machine. In some instances the soap may be extruded in form of a tube or hollow bar, but it should be understood that the present invention is intended to include all such variations.

As above indicated, incomplete expulsion of the air from between the soap particles results in crack formation in the finished bar. Of course, the pressure under which the soap is kneaded and forced forward through the deaerating zone plays an important part in the rate and completeness of air expulsion, higher pressures favoring a higher rate and consequently greater completeness in a given machine. In order to obtain the desired high working pressure in the deaerating Zone, workers in the art have heretofore employed a perforated plate between the deaerating and welding zones to offer suflicient resistance to theA flow of the soap whereby adequate pressure is built up for the rapid and complete expulsion of entrained air, no enlarged welding zone such as that offered by extension II used herein being employed.

Now in my work in the plodding of plastic milled soap, I have discovered that the presence of the perforated plate in theplodding machine sometimes operates so as to defeat its own purpose. It has been my observation that although the entrained air is substantially completely removed from the soap, thereby eliminating one source of crack formation, cracking may result from another cause directly due to the presence of the perforated plate. Friction of the soap in passing through the orifices in the perforated plate, I have found, momentarily heats up the outer surface of the individual rods thus formed sufficiently to change the crystalline structure of the outer surface, as is evident from the smooth polished appearance of same. In this crystalline form the soap film on the exterior of the rods is not easily welded together with similar lms on other soap rods and consequently there often exist in the extruded soap, and in the final bar, cleavage surfaces in the interior thereof corresponding to the intersections of the outer surfaces of the individual small soap rods formed by the perforated plate. Alternate wetting and drying of the bar, which naturally takes place in washstand use, causes alternate expansion and contraction of the soap and consequent cracking at the weakest points or along the aforementioned surfaces of imperfect welding.

It should be noted also that the presence of the perforated plate in the conventional plodder causes a drop in pressure as the soap passes from the deaerating zone to the plodder nose so that the pressure in the welding zone is unavoidably considerably lower than in the deaerating zone. Of course, a high pressure is necessary in the welding zone in order to secure complete welding together of the individual soap rods and therein the conventional plodder is deficient.

The essence of the present invention lies in the omission of the perforated plate and the provision for an equivalent resistance to the flow of the soap which comprises increasing the welding zone volume by inserting an extension Il between the tapered section I6 and the extrusion die I8 of the plodder as illustrated in Figure l, or by inserting an extension I1 between the worm barrel H and the tapered section I6, as illustrated in Figure 2, so that the increased frictional resistance due to passage through the said extension will build up a suiiicient pressure at the end of the deaerating chamber to effect satisfactory air expulsion from between the soap particles. Of course, other types of extensions which are or are not tapered throughout may be employed without departing from the spirit of my invention. Furthermore it is within the scope of my invention to provide such extensions with jackets through which a temperature regulating medium may be passed, or to provide similar means for temperature regulation.

The elimination of the plodder head restrictions such as the perforated plate and the substitution of an extended or elongated unobstructed welding zone to build up an equivalent resistance, or at least sufficient resistance to effect desired air expulsion, result in a number of advantages which directly or indirectly materially reduce the tendency of the milled and plodded soap bars to crack. These advantages are:

l. Elimination of change in crystalline structure of the surface of the soap on passage through the perforated plate and consequent improvement in welding;

2. Elimination of substantial pressure drop as the soap passes from the deaerating zone to the welding zone;

3. Increase in pressure in the welding zone; and

4. Increase in volume of welding zone and consequent increase in the time that the soap is held under pressure for welding.

The length of the extensions used in the construction of a plodder in accordance with my invention will, of course, vary with the size of plodder used and with the type of milled soap being plodded. I have found, for example, that in the plodding of an average type of milled soap, such as the sodium soap prepared from a fat mixture consisting of twenty-five per cent coconut oil and seventy-five per cent tallow or equivalent, and containing about twelve to fifteen per cent of moisture, with a plodder having a barrel diameter of 12 inches, and a barrel extension such as that shown in Figure 2, also of l2 inches diameter and about 36 inches in length, the perforated plate may be omitted and that an improved type of plodded soap substantially free of the tendency to crack will result. Likewise I have found in the plodding of a milled soap such as the above that an extension about 2% inches in diameter and 27 inches in length, such as that shown in Figure 1, will offer sufiicient resistance and will result in a similar improved type of milled soap product. In general, in a plodder for use on the average type of milled soap the ratio of the length to the average diameter of the elongated welding chamber should be at least 3, with an average diameter not less than that of the extrusion orifice.

My observations on the pressures developed within the plodder have shown that at the end of the departing zone, a pressure of about 200 to about 300 pounds per square inch is developed and that at the point of extrusion of the soap through the die, the pressure developed is usually approximately 50 pounds per square inch. Of course, these figures may Vary depending upon the character of the soap being plodded. However, in any event sufficient pressure is employed to effect substantially complete air expulsion from between the soap particles and perfect welding of the soap.

It is clear that without the perforated plate and with the elongated welding zone of my apparatus the pressure in the welding zone will be much higher and will approximate much more closely thepressure in the deaerating zone than is possible in the conventional type plodder. Furthermore, it is clear that the soap will be held under the higher pressure for a suicient time to effect a more perfect welding of the soap into a truly homogeneous mass than has been possible in the conventional type of plodders, especially when handling soap made from fats of relatively high titer.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In the process of plodding milled soap to form a homogeneous bar, in which process the soap is deaerated under superatmospheric pressure, the steps of kneading the soap and forcing same toward an extrusion orice against opposing superatmospheric deaerating pressure, and passing the soap through an unobstructed elongated welding zone in its path to the extrusion orice, the said deaerating pressure being caused mainly by frictional resistance to the passage of the soap through said welding zone and being substantially greater than that required for extrusion alone, so that the flow of the soap from the kneading and forcing zone to and through the welding zone is Without such obstruction as would divide the soap into lamentary parts having diflicultly weldable surfaces which would result in cleavage planes in the extruded product.

2. The step in the process of claim l, in which the superatmospheric pressure in the deaerating zone is above two hundred pounds to the square inch.

BRUCE STRAIN. 

